Apparatus and method for shifting the phase of microwaves

ABSTRACT

Microwave phase shift is obtained by using a liquid dielectric provided by a polymer solution through which the microwaves propagate and across which a controllable electric field is established.

United States Patent [191 Buscher 11] 3,805,197 [451 Apr. '16, 1974 APPARATUS AND METHOD FOR SHIFTING THE PHASE OF MICROWAVES Inventor: Harold T. Buscher, Albuquerque, N.

Mex.

Assignee: General Dynamics Corporation, St.

- Louis,. Mo.

Filed: Mar. 23, 1973 Appl. No.: 344,462

US. Cl. 333/31 A, 333/21 A, 333/98 R Int. C1....- H0311 7/36, H0113 1/18 Field of Search 333/21 A, 31 A, 98 S, 98 R;

. References Cited UNITED STATES PATENTS 4/1971 l lovakm 350/160 l I L 3,631,501 Buscher.

Primary Examin erJa '.mes W. Lawrence Assistant Examiner-Marvin Nus'sbaum Attorney, Agent, or FirmMar ti n Luk'acher ABSTRACT Microwave phase shift is obtained by using a liquid dielectric provided by a polymer solution through which the microwaves propagate and across which a controllable electric field is established.

18 Claims, 3 Drawing Figures Forlini 350/160 R X FIG].

PATENTEUAPR 16 I974 FIGJ APPARATUS AND METHOD FOR SHIFTING THE PHASE OF MICROWAVES The present invention relates to apparatus and methods for controlling the phase of electromagnetic waves and particularly to an electro-optical control system for microwaves.

The present invention is especially suitable for use in providing a microwave phase shifter which is electronically controllable. Aspects of the invention will also be applicable generally for the control or steering OfIClCC- tromagnetic radiation.

The present invention is an improvement over the microwave phase shift apparatus described in U.S. Pat. No. 3,631,501 issued on Dec. 28, 1971 to Harold T. Buscher, for Microwave Phase Shifter with Liquid Dielectric Having Metallic Particles In Suspension. Such a device is also described in an article entitled Phase Varied with Liquid Artificial Dielectric" which appeared in Microwaves Magazine, February 1972, page 9.

Reference may be had to the aforementioned patent and article for a discussion of the applications for microwave phase shifters which may be provided in accordance with this invention and what is believed to be the theoretical bases for their operation.

In essence, the aforementioned patent and articles describe devices containing liquid-solid suspensions in which electric fields control birefringence of a liquid dielectric, operating in accordance with the Kerr effect, the applied electric field polarizesand orders the suspended particles, thus achieving variable microwave birefringence as a result of the induced polarization and alignment of the minute solid components therein.

It has been found in accordance with the invention that liquids containing certain solutions of polymers provide similar effects as the minute solid particles, and eliminate settling of the solid particles and enhance the birefringence and its concomitant phase shift. Thus, the invention provides a new class of artificial dielectrics which maybe used in various microwave devices such as lenses, power dividers, switches, electrically tunable cavities, and phase shifters. Other applications of this new class of dielectrics in electronically controlling electromagnetic radiation, will also undoubtedly suggest themselves to those skilled in the art.

It is therefore an object of the present invention to provide improved methods and means for controlling electromagnetic waves.

It is a further object of the present invention to provide an improved microwave phase shifter.

It is a still further objectof the present invention to provide improved methods and means for shifting the phase of microwavesl It is a still further object of the present invention to provide improved methods and means for controlling microwaves and other forms of electromagnetic radiation with the aid of liquid dielectrics.

Briefly described a microwave phase shifter embodying the invention utilizes a liquid dielectric provided by a solution of a polymer in a solvent. The polymer is selected from the class of polypeptides, polyisocyanates, and azoxydiphenetoles C H 0C, H N:N(:O) C., H., 0C H The solvent is desirably an organic solvent such as benzene or carbon tetrachloride. An electric field is established across-the liquid dielectric and is controlled in intensity so as to vary the phase shift. The

The foregoing and other objects and advantages of the present invention will become more readily apparent from a reading of the following description in connection with the accompanying drawings in which:

FIG. 1 is a front view, partially broken away, of a microwave phase shifter embodying the invention; 7

FIG. 2 is a sectional view of the phaseshifter shown in FIG. 1, the sectionbeing taken along the line 22 in FIG. 1; and

FIG. 3 is a sectional view of the phase shifter shown in FIG. 1, the section being taken along the line 3-3 in FIG. 1;

Referring to FIG. 1, there'is shown a waveguide microwave phase shifter in accordance with the invention. A rectangular guide section 10 has top and bottom walls 12 and 14 and side walls 16 and 18 (see FIG. 2). The guide section 10 has end flanges 20 and 22. A pair of panels 24 and 26 are disposed on the inner surface of the sidewalls. These panels are of insulating material, such as polytetr afluorethylene, commonly known as Teflon, a tradename'of the E. I. Dupont de Nemours Co., of- Wilmington, Del. The opposite ends of the panels 24 and 26 are'tapered for impedance matching purposes. A sheet 28 of conductive material, such as copper, is disposed midway between the top and bottom walls 12 and 14 and is secured along its opposite edges in the panel 24 and 26. A lead 30 is connected through an insulated feed-through terminal 32 which extends to the side wall 18 and the panel 26 to make electrical contact with the sheet 28. The feedthrough terminal 32. provides a liquid seal and also insulates the terminal from the sidewall 18. A source of electric control signals which may'either be direct current or alternating current signals as described in the above referenced patent, is connected between the lead 30 and any point on the wall of the wave guide 10.

. Adjacent wave guide sections 34 and 36 are connected to the section 10 through liquid seals 39, which are provided by Teflon sheet 39. The sheet is a flange which extends from an impedance matchingsection in the form of a bilaterally tapered wedge 38. A similar impedance matching wedge may be provided between the section 10 and the waveguide section 36 at the opposite end of the section 10. I

A liquid dielectric is contained in the wave guide section 10. This liquid dielectric consists of a polymer solution. Certain polymers which provide :1 Kerr effect in solution have been found to be satisfactory. These polymers are polypeptides, polyisocyanates, and azoxydiphenetoles. The polypeptides have the structural formula:

In these formulas R is an alkyl, an amino, a hydroxy or any substituted alkyl, including a carboxy substituted alkyl. The'following polypeptides are suitable. Poly-'y-benzyl-L-glutamate, poly-methyl-L-glutamate, poly-B-benzyl-L-aspartate, polyglutamic acid, and

-carboxybenzyl-L-lysine. Poly-benzyl-L- in accordance with the following example:

glutamate isespecially suitable. This material is also known as PBLG. For'PBLG, R is represented by the following structural formula:

The foregoing polymers are characterized by being of any molecular weight which provides a value of n in the structural formula which has a measurable Kerr effect. Kerr efi'ectmay bemeasured by the OKonski method. For PBLG, a suitable value of n is approximately equal to 2,000, the material having a molecular weight measured by the viscosity techniques of 3 X 10 The liquid dielectric solution may be made in accordance with the following example:

250 milligrams of PBLG (molecular weight, approximately equal .to 240,000 as measured by the viscosity techniques) is dissolved in 25 ccs ofcarbon tetrachloride CCl To assist in dissolving the PBLG, the solution is ultrasonicly agitated and heated to about 35C, such agitation and heat being applied for approximately minutes. Alternatively, the solvent may be 25 ccs of benzene (C H ultrasonic agitation and heating being applied as aforementioned in the case of carbon tetrachloride. When microwave energy at a frequency of 16.5 Gl-lz at room temperature is propagated through the phase shifter illustrated in FIG. 1 and a kilovolt per centimeter direct current field is applied, a phase shift of two-tenths of a degree between the wave-guide ends (the wave-guide being approximately 12.5 centimeters long) is obtained for the solution, either in carbon tetrachloride or in benzene.

The polymer may also be a polyisocyanate. Such polymers are also called l-nylon polymers. The polyisocyanates are represented by the structural formula:

R in the formula can be any of the following side chain groups, methyl, ethyl, butyl, hexyl, undecyl,

phenyl, benzyl, naphthyl, unde cenyl, nitrophenyl, ethoxy, chlorophenyl. Accordingly, R can be any alkyl, alkenyl, or any substituted alkyl, or alkenyl. In the structural formula n is a large whole number, typically 400.

1 gram of p,p azoxydiphenetole, which may be procured in the form of liquid crystals from Eastman Chemical Company, at Kingsport, Tenn., is dissolved in 60 millimeters of carbon tetrachloride (CCl To assist the azoxydiphenetole going into solution, heat (35C) and ultrasonic agitation is applied for approximately 10 minutes. Measured under the same conditions as was discussed abovein connection with the example for PBLG, 04 of phase shift was measured.

' As another example:

5 grams of p,p' azoxydiphenetole was dissolved in millimeters of benzene (C l-l using ultrasonic agitation and heating as described above. The solution when contained in the phase shifter shown in FIG. 1 provided 01 of phase shift under the same test conditions as discussed in the case of the exemplary PLBG solution. I 1 From the foregoing description, it willbe apparent that there has been provided improved methods and means for electronically controlling electromagnetic radiation, especially microwaves. A new class of dielectric liquids and methods of using same has been described, particular examples and formulations being given to illustrate the invention. Variations and modifications in the herein described examples and materials,

within the scope of the invention will undoubtedly sug: gest themselves'to those skilled in the art. Accordingly, the foregoing description should be taken merely as illustrativeand not in any limiting sense.

What is claimed is:

l. Electromagnetic wave control apparatus which comprises means containing a liquid consisting of a solution of a polymer selected'from the class of polypeptides, polyisocyanates, andazoxidiphenetoles dissolved in a solvent, and means for applying an electric field across said solution for shifting the phase of said electromagnetic wave as it propagates therethrough.

2. The invention as set forth in claim 1 wherein said polymer is a polypeptide having the structural formula polypeptide is Poly-y-Benzyl-L-Glutamate, also known as PBLG.

5. The invention as set forth in claim Z wherein R is defined by the structural formula polymer is p,p'- azox'ydiphenetole.

1 0. The method of phase shifting microwaves which- 6 wherein R is selected from the class of alkyl, amino, hy-

droxy, and substituted alkyl groups.

comprises transmitting said waves through a liquid consisting of a solution of a polymer selected from the class of polypeptides, polyisocyanates, and phenetoles dissolved in a solvent, and establishing an electric field in said liquid.'

11. The invention asset forth in claim 10 wherein said polymer is a polypeptide having. the structural forazoxydi- 12. The invention as set forth in claim 11 wherein n is of a value such that said solution provides a measurable Kerr effect constant. g

13. The invention as set forth in claim 11 wherein said Polypeptide is Poly'y-Benzyl-L-Glutamate, also known as PBLG.

14. The invention as set forth in claim 11 wherein-R is defined by the structural formula 15. The invention as set forth in claim 6 wherein said solvent is characterized by high transparency to microwave radiation.

. said solvent is an organic solvent.

16. The invention as set forth in claim 15 wherein 17.The invention as set forth in claim 16 wherein said solvent is selected from benzene (C H and carbon tetrachloride (CCl 18. The invention as set forth'in claim ll wherein said polymer is p,p'-- azoxydiphenetole. 72s 

1. Electromagnetic wave control apparatus which comprises means containing a liquid consisting of a solutIon of a polymer selected from the class of polypeptides, polyisocyanates, and azoxidiphenetoles dissolved in a solvent, and means for applying an electric field across said solution for shifting the phase of said electromagnetic wave as it propagates therethrough.
 2. The invention as set forth in claim 1 wherein said polymer is a polypeptide having the structural formula
 3. The invention as set forth in claim 2 wherein n is of a value such that said solution provides a measurable Kerr effect constant.
 4. The invention as set forth in claim 1 wherein said polypeptide is Poly- gamma -Benzyl-L-Glutamate, also known as PBLG.
 5. The invention as set forth in claim 2 wherein R is defined by the structural formula
 6. The invention as set forth in claim 1 wherein said solvent is characterized by high transparency to microwave radiation.
 7. The invention as set forth in claim 6 wherein said solvent is an organic solvent.
 8. The invention as set forth in claim 7 wherein said solvent is selected from benzene (C6 H6) and carbon tetrachloride (CCl4).
 9. The invention as set forth in claim 1 wherein said polymer is p,p''- azoxydiphenetole.
 10. The method of phase shifting microwaves which comprises transmitting said waves through a liquid consisting of a solution of a polymer selected from the class of polypeptides, polyisocyanates, and azoxydiphenetoles dissolved in a solvent, and establishing an electric field in said liquid.
 11. The invention as set forth in claim 10 wherein said polymer is a polypeptide having the structural formula
 12. The invention as set forth in claim 11 wherein n is of a value such that said solution provides a measurable Kerr effect constant.
 13. The invention as set forth in claim 11 wherein said Polypeptide is Poly gamma -Benzyl-L-Glutamate, also known as PBLG.
 14. The invention as set forth in claim 11 wherein R is defined by the structural formula
 15. The invention as set forth in claim 6 wherein said solvent is characterized by high transparency to microwave radiation.
 16. The invention as set forth in claim 15 wherein said solvent is an organic solvent.
 17. The invention as set forth in claim 16 wherein said solvent is selected from benzene (C6 H6) and carbon tetrachloride (CCl4).
 18. The invention as set forth in claim 11 wherein said polymer is p,p''- azoxydiphenetole. 